In an apocalyptic vision portending worldwide coastal flooding presented by National Geographic in its September issue, Long Island disappears under the Atlantic Ocean. Not just the north or south shores, the East End wine region, the posh Hamptons, Queens or Brooklyn –– all of it.

It is a stark picture, depicted as only National Geographic can in a brilliantly detailed fold-out map. The magazine’s editors, writers and cartographers imagine a world in which all the land-based ice locked up in Greenland, the Antarctic and glaciers melts into the sea. It isn’t a pretty picture.

According to the magazine, there are more than 5 million cubic miles of ice on Earth. Since the start of the Industrial Revolution, around 1750, people have burned fossil fuels –– coal, oil and natural gas –– at an increasingly alarming rate, sending more than 300 billion of tons of carbon dioxide into the atmosphere to date, raising the global mean temperature and setting in motion the phenomenon known as climate change, a.k.a. global warming.

We need only look to the U.S.’s northern climes, where temperatures soared past 100 degrees in long-term heat waves this summer, sending normally wet states into drought, to understand that something is amiss with Mother Earth.

Ice, obviously, melts faster in a warmer world than it does in a cooler one. The questions are, how long will it be before all of the land-based ice melts into the oceans, and if it does all melt, how high would the seas rise?

No one, according to National Geographic, knows precisely when it might all disappear. It could be 5,000 years, but at the rate we’re burning fossil fuels, it could be much sooner, perhaps within hundreds of years.

One thing is for sure: If we burn all of the Earth’s fossil fuels, all the ice will someday be gone, raising the world’s oceans by 216 feet, National Geographic says. That’s because the average worldwide temperature would no longer be 58 degrees Fahrenheit, as it is now, but could jump past 80 degrees. On such an Earth, whole regions of the planet might never fall below 100 degrees.